I need to know some of the most credible book conventions or just
somewhere to promote a book. I live in massachusetts, but anywhere in
the states will do, or any other english speaking countries. The
subject of the book is nutrition and exercise if that helps. I'd also
take some CREDIBLE online methods as well.

Hi! Thanks for the question.

I have found the following link from About.com that lists popular book
fairs in the world. Two of them are in the US.

About.com: Book Fairs
http://publishing.miningco.com/cs/bookfairs/ 

I will provide you with direct links to the conventions listed above
since some of the links are not working.

US:

BookExpo America
http://www.bookexpo.reedexpo.com/App/homepage.cfm?moduleid=42&appname=288

Miami Book Fair International
http://www.mdcc.edu/bookfair/index.htm 

Abroad:

Asia International Book Fair
http://www.aibf.com.sg/ 

Frankfurt Book Fair
http://www.frankfurt-book-fair.com/en/portal.html 

London Book Fair
http://www.lbf-virtual.com

Jerusalem Book Fair
http://www.jerusalembookfair.com/

Zimbabwe International Book Fair
http://www.zibf.org/

Other book fairs I found are listed below:

Northwest Book fest (US)
http://www.nwbookfest.org/ 

Book Expo Canada
http://www.reedexpo.ca/bookexpo/ 

My next link provides a big list of international book fairs for 2003.

“World Book Fair Calendar 2003”
http://apm.brookes.ac.uk/sulaiman/bellagio/events/bookfairs2003.htm 

--------------------
Since you said that you are interested in other book promotion ideas,
here are the things I found online.

“How to promote a book for free” (online promotion tips)
http://wvwv.essortment.com/freebookseb_rmgs.htm 

“Book Promotion for the Shameless”
http://www.spilledcandy.com/Shameless.html 

“GETTING BOOKED AND PRINTED”
http://pw1.netcom.com/~tpwarner/tips.htm 

“FREE Articles on Book Promotion, Marketing, & Publicity “
http://members.aol.com/spilledcandybks/library.html 

“How to prepare a book promotion package”
http://ksks.essortment.com/bookpromotion_rlio.htm

“Ways to promote your book”
http://iaia.essortment.com/promoteyourboo_rlme.htm 

Search terms used:   
book trade shows -comic
"book promotion" tips
                  
I hope these links would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
                  
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Regards,                   
Easterangel-ga                   
Google Answers Researcher